The present disclosure relates, in various embodiments, to thin-film transistors (TFTs) and/or other electronic devices comprising a dielectric layer. The dielectric layer is formed from a dielectric composition as described herein that includes a thermal acid generator. This allows the dielectric composition to be cured at a lower temperature and for a shorter period of time, enabling the use of roll-to-roll manufacturing and other processes.
TFTs are generally composed of, on a substrate, an electrically conductive gate electrode, source and drain electrodes, an electrically insulating gate dielectric layer which separates the gate electrode from the source and drain electrodes, and a semiconducting layer which is in contact with the gate dielectric layer and bridges the source and drain electrodes. Their performance can be determined by the field effect mobility and the current on/off ratio of the overall transistor. High mobility and high on/off ratio are desired.
Organic thin-film transistors (OTFTs) can be used in applications such as radio frequency identification (RFID) tags and backplane switching circuits for displays, such as signage, readers, and liquid crystal displays, where high switching speeds and/or high density are not essential. They also have attractive mechanical properties such as being physically compact, lightweight, and flexible.
Organic thin-film transistors can be fabricated using low-cost solution-based patterning and deposition techniques, such as spin coating, solution casting, dip coating, stencil/screen printing, flexography, gravure, offset printing, ink jet-printing, micro-contact printing, and the like, or a combination of these processes. Such processes are generally simpler and more cost effective compared to the complex photolithographic processes used in fabricating silicon-based thin-film transistor circuits for electronic devices. To enable the use of these solution-based processes in fabricating thin-film transistor circuits, solution processable materials are therefore required.
In this regard, gate dielectric layers may be formed by these solution-based processes. However, the gate dielectric layer so formed should be free of pinholes and possess low surface roughness (or high surface smoothness), low leakage current, a high dielectric constant, a high breakdown voltage, adhere well to the gate electrode, and offer other functionality. It should also be compatible with semiconductor materials because the interface between the dielectric layer and the organic semiconductor layer critically affects the performance of the TFT.
Roll-to-roll manufacturing refers to the process, still somewhat in development, of creating electronic devices on a roll of flexible plastic or metal foil, similar to the gravure, offset, and flexographic printing processes used with paper. It is contemplated that large circuits made with thin-film transistors and other devices can be easily patterned onto these large substrates, which can be up to a few metres wide and 50 km long. This type of manufacturing would allow for large-scale low-cost devices, especially when compared to normal semiconductor manufacturing processes that use photolithography techniques on inch-size silicon wafers.
Low temperatures and increased speed of processing are critical to roll-to-roll manufacturing. It would be desirable to provide a dielectric layer and/or dielectric composition that could be processed at lower temperatures and/or shorter time periods, to allow for manufacture of an electronic device using roll-to-roll manufacturing and other processes.
It would be also desirable to have a dielectric composition with good shelf-life at room temperature, which cures or crosslinks quickly at an elevated temperature.